To the best of our knowledge, we live in a physical reality with matter that abides by certain laws.
So personal beliefs aside, it's a safe starting assumption that human brains also operate with these primitives.
A Turing machine is a model of computation which was in part created so that "a human could trivially emulate one". (And I'm not talking about the Turing test here). We also know that there is no stronger model of computation than what a Turing model is capable of -> ergo anything a human brain could do, could in theory be doable via any other machine that is capable of emulating a Turing machine, be it silicon, an intricate game of life play, or PowerPoint.
It's better to say we live in a reality where physics provides our best understanding of how that fundamental reality behaves consistently. Saying it's "physical" or follows laws (causation) is making an ontological statement about how reality is, instead of how we currently understand it.
Which is important when people make claims that brains are just computers and LLMs are doing what humans do when we think and feel, because reality is computational or things to that effect.
There are particular scales of reality you don't need to know about because the statistical outcome is averaged along the principle of least action. A quantum particle could disappear, hell maybe even an entire atom. But any larger than that becomes horrifically improbable.
I don't know if you've read Permutation City by Greg Egan, but it's a really cool story.
Do I believe we can upload a human mind into a computing machine and simulate it by executing a step function and jump off into a parallel universe created by a mathematical simulation in another computer to escape this reality? No.
It's a neat thought experiment but that's all it is.
I don't doubt that one day we may figure out the physical process that encodes and recalls "memories" in our minds by following the science. But I don't think the computation model, alone, offers anything useful other than the observation that physical brains don't load and store data the way silicon can.
Could we simulate the process on silicon? Possibly, as long as the bounds of the neural net won't require us to burn this part of the known universe to compute it with some hypothetical machine.
That's a very superficial take. "Physical" and "reality" are two terms that must be put in the same sentence with _great_ care. The physical is a description of what appears on our screen of perception. Jumping all the way to "reality" is the same as inferring that your colleague is made of luminous RGB pixels because you just had a Zoom call with them.
So personal beliefs aside, it's a safe starting assumption that human brains also operate with these primitives.
A Turing machine is a model of computation which was in part created so that "a human could trivially emulate one". (And I'm not talking about the Turing test here). We also know that there is no stronger model of computation than what a Turing model is capable of -> ergo anything a human brain could do, could in theory be doable via any other machine that is capable of emulating a Turing machine, be it silicon, an intricate game of life play, or PowerPoint.